STACK Documentation

Buggy rules

In order to establish that the student has done something
particular but wrong, it is useful for us to be able to apply
wrong or buggy rules to expressions. A typical example would
be to expand out powers in the wrong way, e.g.

Naive addition of fractions

Note that both denom and num work on non-rational expressions, assuming the expression to be "over one" by implication. Hence mediant will also assume the denominator is also one in such cases.

This is not always a buggy rule. It is used, for example, in connection with Farey sequences, but it is included here as in assessment this function is useful for checking a common mistake when adding fractions.